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Abstract:

The present invention provides a method for installing a hydroelectric
turbine at a deployment site on the seabed which involves lowering the
turbine and associated base onto the seabed from a vessel using a number
of lines, and once on the seabed using these lines to tether the vessel
to the base/turbine while telemetry from the base/turbine is analysed.

Claims:

1. A method of installing a base (12) and a hydroelectric turbine (10)
onto the seabed, the method comprising the steps of:connecting the
turbine (10) to the base (12);transporting the base (12) and turbine (10)
to a deployment site by a deployment vessel (14);lowering the base (12)
onto the seabed from the vessel (14);keeping the vessel (14) tethered to
the base (12);establishing the suitability of the installation;
anddisconnecting the vessel (14) from the base (12).

2. A method according to claim 1 comprising lowering the base (12) by
means of a number of lowering lines (22) fed from the deployment vessel
(14).

3. A method according to claim 2 comprising the step of feeding slack into
the lowering lines (22) once the base (12) is located on the seabed.

4. A method according to claim 1 comprising lowering the base (12) onto
the seabed in flowing water.

5. A method according to claim 1 comprising lowering the base (12) onto
the seabed in a tidal stream, an ocean current or a running river.

6. A method according to claim 4 comprising the step of substantially
maintaining the position of the deployment vessel (14) against the
flowing water.

7. A method according to claim 1 comprising the step of receiving
telemetry from the base (12) and/or turbine (10) prior to the final
positioning on the seabed.

8. A method according to claim 1 comprising, in the transporting step,
towing the deployment vessel (14) to the deployment site.

9. A method according to claim 8 comprising the step of slackening a
tow-line between the towing vessel and the deployment vessel (14)
following slackening of lowering lines (22) between the vessel (14) and
the base (12).

10. A method according to claim 1 comprising, in the step of establishing
the suitability of the installation, receiving telemetry from the base
(12) and/or turbine (10) when on the seabed.

11. A method according to claim 1 comprising, in the lowering step,
lowering the base (12) from directly beneath the vessel (14).

12. A method according to claim 1 comprising the step of tethering the
base (12) to an anchor upstream of the deployment site prior to lowering
the base (12) from the vessel (14).

13. A method according to claim 1 comprising the further step of at least
partially raising the base (12) off the seabed and repositioning same
prior to disconnecting the vessel (14) from the base (12).

Description:

FIELD OF THE INVENTION

[0001]The present invention is concerned with a method of installing a
hydroelectric turbine onto the seabed, and in particular a method which
enables the hydroelectric turbine to be pre-installed on a base prior to
the installation, thereby greatly simplifying the installation process.

BACKGROUND OF THE INVENTION

[0002]Due to the environmental damage which has been inflicted on the
planet as a result of the burning of fossil fuels, renewable energy has
finally begun to be given significant attention, with many projects being
developed around solar energy, wind energy, and tidal power. Of these
alternative forms of energy, tidal power is arguably the most attractive,
given that tidal flows are entirely predictable and constant, unlike wind
or solar energy which are relatively intermittent and therefore less
dependable.

[0003]However, harnessing tidal energy does provide its own challenges, in
particular with respect to the installation and maintenance of tidal
power generators, for example hydroelectric turbines, which by the very
nature of the operation of same must be located in relatively fast
flowing tidal currents, and more than likely located on the seabed. In
addition, in order to be economically viable these turbines must be built
on a large scale. As a result the turbines and associated bases/supports
are large and cumbersome components, and require significant heavy
lifting and transport equipment in order to achieve deployment. The use
of such heavy lifting equipment is normally a hazardous undertaking, and
is rendered even more dangerous when this equipment is operated at sea
under difficult and unsteady conditions. In addition, most installations
of such tidal generating equipment consists of the fixing of one or more
piles into the seabed as a first phase of the installation, and then as a
second phase installing one or more turbines onto the pile(s). The
sinking of a pile into the seabed in an area of high tidal flow is
considerably problematic and generally a dangerous operation. In
addition, significant drilling and piling equipment must be transported
to and operated at the site of installation, significantly increasing the
complexity and cost of the operation.

[0004]The installation process is further complicated by an increasing
shortage in the market of suitable vessels and equipment to perform such
drilling work and the extreme danger of engaging divers in high tidal
flow sites.

[0005]As mentioned above, working at sea with such large and heavy
equipment is a dangerous and time consuming operation, and anything that
can be done to simplify this task and/or decrease the time taken is of
great benefit.

[0006]The present invention has therefore been developed with a view to
simplifying the installation of hydroelectric turbines, which method
allows the installation of a hydroelectric turbine which has been
pre-installed on a base.

SUMMARY OF THE INVENTION

[0007]The present invention provides a method of installing a base and a
hydroelectric turbine onto the seabed, the method comprising the steps
of: [0008]connecting the turbine to the base; [0009]transporting the
base and turbine to a deployment site by a deployment vessel;
[0010]lowering the base onto the seabed from the vessel; [0011]keeping
the vessel tethered to the base; [0012]establishing the suitability of
the installation; and [0013]disconnecting the vessel from the base.

[0014]Preferably, the method comprises lowering the base by means of a
number of lowering lines fed from the deployment vessel.

[0015]Preferably, the method comprises the step of feeding slack into the
lowering lines once the base is located on the seabed.

[0016]Preferably, the method comprises lowering the base onto the seabed
in flowing water.

[0017]Preferably, the method comprises lowering the base onto the seabed
in a tidal stream, an ocean current or a running river.

[0018]Preferably, the method comprises the step of substantially
maintaining the position of the deployment vessel against the flowing
water.

[0019]Preferably, the method comprises the step of receiving telemetry
from the base and/or turbine prior to the final positioning on the
seabed.

[0020]Preferably, the method comprises, in the transporting step, towing
the deployment vessel to the deployment site.

[0021]Preferably, the method comprises the step of slackening a tow-line
between the towing vessel and the deployment vessel following slackening
of lowering lines between the vessel and the base.

[0022]Preferably, the method comprises, in the step of establishing the
suitability of the installation, receiving telemetry from the base and/or
turbine when on the seabed.

[0023]Preferably, the method comprises, in the lowering step, lowering the
base from directly beneath the vessel.

[0024]Preferably, the method comprises the step of tethering the base to
an anchor upstream of the deployment site prior to lowering the base from
the vessel.

[0025]Preferably, the method comprises the further step of at least
partially raising the base off the seabed and repositioning same prior to
disconnecting the vessel from the base.

[0026]As used herein, the term "seabed" is intended to mean the seabed in
addition to the base or bottom of any suitable body of water such as a
riverbed or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 illustrates a schematic illustration of a deployment vessel
carrying a base and turbine thereon, having been towed to a deployment
site;

[0028]FIG. 2 illustrates the vessel of FIG. 1 lowering the base and
turbine towards the seabed;

[0029]FIG. 3 illustrates the arrangement of FIGS. 1 and 2 following the
location of the base and turbine on the seabed;

[0030]FIG. 4 illustrates the arrangement of FIG. 3 following the
retraction of the base and turbine from the seabed; and

[0031]FIG. 5 illustrates the base and turbine having been released from
the deployment vessel to begin operation.

DETAILED DESCRIPTION OF THE DRAWINGS

[0032]Referring now to the accompanying drawings, there is described and
shown a method of installing a hydroelectric turbine 10 and associated
base 12 onto the seabed B at a deployment site S. In the embodiment
illustrated, a deployment vessel 14 is utilised to transport the turbine
10 and base 12 to a deployment site S. In this preferred embodiment, the
vessel 14 does not have its own means of propulsion and thus a tug T is
used to tow the vessel 14 to the deployment site S. It will, however, be
appreciated that the vessel 14 could be provided with propulsion means,
such as an inboard or outboard motor(s) or the like (not shown) and in
such a situation the use of the tug T could be omitted. The use of the
tug T is therefore not an essential element of the method of the
invention. In addition, although the turbine 10, base 12 and vessel 14
are each shown as a particular design or configuration it is to be
understood that these are merely examples and not essential to the method
of installation of the invention.

[0033]Prior to proceeding to the deployment site S, the vessel 14 is
preferably towed to a relatively sheltered location such as a nearby bay
or the like, in order to await the correct tidal conditions for
deployment of the turbine 10. The preferred tidal velocity for deployment
is a falling tide, although it will be appreciated that these conditions
are not essential to the method of deployment and merely provide the
ideal working conditions for the method of installation of the invention.
One of the benefits of deployment during a falling tide, as will become
apparent from the following description, is in providing time for the
turbine 10 and base 12 to be returned to the surface during "slack water"
if the installation is to be aborted. In addition a falling tide tends to
keep the vessel 14 in the correct orientation facing into the tide such
that the turbine 10, when lowered to the seabed B, is also facing into
the tide to achieve maximum operating efficiency.

[0034]Once the preferred tidal conditions are present, the vessel 14 is
towed over the deployment site S. At this point, the tug T is faced into
the falling tide F and the speed of the tug T is matched as closely as
possible to the speed of the tide, in order to maintain the position of
the vessel 14 over the site S. The turbine 10 and base 12 are now ready
to be released from the vessel 14. It is however envisaged that the
turbine 10 could be omitted from the base 12, and thus the base 12 would
be lowered to the seabed B in isolation. The turbine 10 would then need
to be suitably located on and fixed to the base 12.

[0035]The base 12 comprises a frame 16 which, in the embodiment
illustrated, is capable of being secured on the underside of the vessel
14, the base 12 having three legs 17 extending downwardly from the frame
16. The base 12 further comprising a pair of supports 18 which project
upwardly from the frame 16. The vessel 14 is adapted to allow the
supports 18 to project upwardly through the vessel 14, onto which
supports 18 the turbine 10 is suitably fixed. A number of winches 20,
three in the embodiment illustrated, are provided on the vessel 14 and
are secured to the frame 16 to be used to raise and lower the base 12
relative to the vessel 14. Locking means (not shown) are preferably
provided on the base 12 and/or vessel 14 in order to allow the base 12 to
be locked securely to the underside of the vessel 14. However the winches
20 may themselves double as this locking means.

[0036]Referring to FIG. 2, once the vessel 14 is positioned over the site
S the locking means (not shown) are released and the winches 20 can then
be used to begin to lower the base 12 and turbine 10 towards the seabed
B. In the embodiment illustrated the turbine 10 can pass directly through
the vessel 14, thereby enabling the base 12 and turbine 10 to be lowered
from directly beneath the vessel 14, providing significant stability
during the lowering process. Each winch 20 feeds out a respective
lowering line 22 connected to the base 12 in order to lower the base 12
towards the seabed B and in particular the installation site S.
Conventionally when lowering such components from a marine vessel it is
necessary to utilise a crane or similar boom based hoist (not shown)
overhanging the side of the vessel. This type of arrangement is
inherently less stable due to the moment of the crane and component
suspended therefrom.

[0037]Once the base 12 is positioned close to the seabed B, without having
contacted same, sensors (not shown) on the base 12 and/or turbine 10 are
used to receive telemetry from the base 12. In particular it is
preferable that the sensors (not shown) are adapted to provide video,
location and depth information to persons co-ordinating the installation,
and who are preferably located on the deployment vessel 14. Once this
telemetric information is deemed within acceptable parameters, the base
12 can be fully lowered onto the seabed B. Again the sensors (not shown)
will provide telemetry to indicate when the base 12 actually contacts the
seabed B.

[0038]Referring to FIG. 3, the tug T now attempts to hold the deployment
vessel 14 in position against the falling tide F while an additional
length of lowering line 22 is unwound from each winch 20, for example an
additional 5 m of line 22 is released. As a result of the slack on the
lines 22 the base 12 will be firmly seated on the seabed B, and the tug T
then eases out the towline L secured between the tug T and the vessel 14
to create slack in the towline L. This arrangement allows the base 12 to
act as an anchor which is tethering the vessel 14 thereto. In this way
the base 12 is allowed to sit on the seabed B entirely under the weight
of the turbine 10 and base 12 while remaining connected to the vessel 14.
If the turbine 10 and base 12 were then required to be raised off the
seabed B for any reason the connection between the vessel 14 and the base
12 would simplify this process.

[0039]As there is now no external loading on the base 12 and turbine 10,
the base 12 should be sitting stably on the seabed B. It is important,
during this phase of the installation, that the tug T does not put any
load on the towline L. At this point, telemetry is taken from the base 12
and studied to confirm how the base 12 is lying on the seabed B.

[0040]Referring to FIG. 4, if the telemetry indicates that the base 12 is
not sitting within agreed parameters, for example, location, direction,
tilt, depth, etc, the base 12 and turbine 10 can be quickly and easily
raised and re-positioned using the winches 20. The slack is taken up from
the lowering lines 22 and the winches 20 then used to draw the base 12
off the seabed B for re-positioning. During this process the tug T is
again used to hold the position of the vessel 14 steady against the
falling tide. Once the base 12 has been lifted, the tug T can be used to
move the vessel 14 to a new location, at which the base 12 can be
re-positioned on the seabed B as hereinbefore described. If during the
positioning of the base 12 it is not possible to complete the
installation within the available window or to the agreed parameters, the
base 12 and turbine 10 can be fully raised back into position and
connected to the vessel 14 to be towed back to harbour.

[0041]In a preferred arrangement the base 12 is lowered such that the
front leg 17 contacts the seabed B before the rear two legs 17. This is
achieved by feeding slightly more lowering line 22 from the font winch
20. Once the front leg 17 contacts the seabed B it can be used as a pivot
on which the base 12 can be rotated in order to allow the orientation of
the base 12 to be varied. By moving the vessel 14 the orientation of the
base 12 can be corrected, and once done the rear two legs 17 can then be
lowered onto the seabed B.

[0042]Referring to FIG. 5, provided that the base 12 is sitting on the
seabed B within agreed parameters, each of the lowering lines 22 can be
disconnected from between the base 12 and the vessel 14 thereby leaving
the base 12 and turbine 10 located at the deployment site S to begin
operation. The tug T can then tow the empty vessel 14 back to harbour.

[0043]The above installation method may be modified by using an anchor
(not shown) to stabilise the base 12 during lowering onto the seabed B.
In particular, the anchor would be laid on the seabed upstream of the
installation site, and would preferably be provided with a buoy tethered
thereto to enable the base 12 to be connected to the anchor while secured
to the vessel 14. Once the vessel is positioned over the deployment site,
the base is tied to the anchor, for example by the front leg 17. Thus as
the base 12 is lowered towards the seabed B the anchor, being upstream of
the base 12, will help to maintain the correct orientation of the base
12.

[0044]The present invention therefore provides a method for installing a
hydroelectric turbine 10 and base 12 onto the seabed B which enables the
installation to be checked before disconnecting the deployment vessel 14.

Patent applications by James Ives, Dublin IE

Patent applications by Paul Dunne, Dublin IE

Patent applications by OPENHYDRO GROUP LIMITED

Patent applications in class With assembly of sectional supporting structure at site

Patent applications in all subclasses With assembly of sectional supporting structure at site